Search Results for: classify of lncrna

It was traditionally thought that the transcriptome would be mostly comprised of mRNAs, however advances in high-throughput RNA sequencing technologies have revealed the complexity of our genome. Non-coding RNA is now known to make up the majority of transcribed RNAs and in addition to those that carry out well-known housekeeping functions (e.g. tRNA, rRNA etc), many different types of regulatory RNAs have been and continue to be discovered. Many of these non-coding RNAs are thought to have a wide range of functions in cellular and developmental processes.

Long noncoding RNAs (lncRNAs) are a large and diverse class of transcribed RNA molecules with a length of more than 200 nucleotides that do not encode proteins. Their expression is developmentally regulated and lncRNAs can be tissue- and cell-type specific. A significant proportion of lncRNAs are located exclusively in the nucleus. They are comprised of many types of transcripts that can structurally resemble mRNAs, and are sometimes transcribed as whole or partial antisense transcripts to coding genes. LncRNAs are thought to carry out important regulatory functions, adding yet another layer of complexity to our understanding of genomic regulation.

Figure 1 A summary of the various functions described for lncRNA. (Click for a larger image)

Large noncoding RNAs are emerging as an important component in cellular regulation. Considerable evidence indicates that these transcripts act directly as functional RNAs rather than through an encoded protein product. However, a recent study of ribosome occupancy reported that many large intergenic ncRNAs (lincRNAs) are bound by ribosomes, raising the possibility that they are translated into proteins.

Here, researchers from the Broad Institute of MIT and Harvard show that classical noncoding RNAs and 5′ UTRs show the same ribosome occupancy as lincRNAs, demonstrating that ribosome occupancy alone is not sufficient to classify transcripts as coding or noncoding. Instead, they define a metric based on the known property of translation whereby translating ribosomes are released upon encountering a bona fide stop codon. They show that this metric accurately discriminates between protein-coding transcripts and all classes of known noncoding transcripts, including lincRNAs. Taken together, these results argue that the large majority of lincRNAs do not function through encoded proteins.

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Long non-coding RNAs (lncRNAs) have been found to perform various functions in a wide variety of important biological processes. To make easier interpretation of lncRNA functionality and conduct deep mining on these transcribed sequences, it is convenient to classify lncRNAs into different groups. Here, researchers from the CAS Key Laboratory of Genome Sciences and Information, China summarize classification methods of lncRNAs according to their four major features, namely, genomic location and context, effect exerted on DNA sequences, mechanism of functioning and their targeting mechanism. In combination with the presently available function annotations, they explore potential relationships between different classification categories, and generalize and compare biological features of different lncRNAs within each category. Finally, they present our view on potential further studies. The researchers believe that the classifications of lncRNAs as indicated above are of fundamental importance for lncRNA studies, helpful for further investigation of specific lncRNAs, for formulation of new hypothesis based on different features of lncRNA and for exploration of the underlying lncRNA functional mechanisms.

What is lncRNA?

Long non-coding RNAs (long ncRNAs, lncRNA) are in general considered (somewhat arbitrarily) as non-protein coding transcripts longer than 200 nucleotides. While long ncRNAs are located and transcribed within the intergenic stretches, the majority are transcribed as complex, interlaced networks of overlapping sense and antisense transcripts that often includes protein-coding genes. Recent recognition that long ncRNAs function in various aspects of cell biology has focused increasing attention on their potential to contribute towards disease aetiology. A handful of studies have implicated long ncRNAs in a variety of disease states.

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